Yagyu-shinkage ryu swordsmanship I think derived from a single family's experience in defending their lands from intruders. It grew to a system that encompassed a hugely diverse set of skills, as suggested by Thalib

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b) a martial art losing touch with its roots and becoming just a form of self-defence and/or dance (and leave ki aikido out of this one you traditionalists)?

I would submit Jeet Kune Do as an example of just self defense. Its practitioners would likely disagree, as Bruce Lee was personally very philosophical/spiritual.

For dance I would suggest any of the myriad and prolific "McDojo's". Pick an art, it's represented.